Bifunctional ZnMn2O4/reduced graphene oxide microspheres with a needle-like surface architecture as effective electrodes for energy storage

Abstract

The synthesis of bifunctional electrode materials is of tremendous interest for energy storage applications. A simple hydrothermal route is chosen to develop reduced graphene oxide encapsulated zinc manganite microspheres (ZnMn₂O₄/rGO). Microspheres with a needle-like surface architecture could be produced by carefully regulating the process parameters during synthesis and post-annealing. The ZnMn₂O₄/rGO composite exhibited a specific surface area of 67.82 m² g⁻¹. The ZnMn₂O₄/rGO composite electrode demonstrated bifunctional behavior for both lithium-ion batteries and supercapacitors. As an anode, it displayed exceptional discharge/charge capacity of 1578/1012 mA h g⁻¹ at a current density of 0.1 A g⁻¹ and maintained stable cycling behavior even after 300 cycles at a current density of 1 A g⁻¹. Moreover, it showed excellent capacitive behavior with a specific capacity of 100.5 mA h g⁻¹ at 1 A g⁻¹ and maintained a cycling stability of 83% at 2 A g⁻¹ even after 5000 cycles. Therefore, ZnMn₂O₄/rGO composites are promising candidates for practical applications in energy storage.